Developing mobile terminal apparatuses equipped with azimuth measuring function has been conducted in recent years. A magnetic sensor is utilized for the measurement of an azimuth. These mobile terminal apparatuses display a present position and the like on a map shown on the screen using an azimuth measured according to positional information from GPS (Global Positioning System).
The magnetic sensor detects not only natural magnetic fields but also dynamic magnetic fields generated by the interior of the mobile terminal apparatus as well as by nearby electrical equipment or the like. Hence, in order to extract natural magnetic field component only, it is necessary to delete the dynamic magnetic components from the detected magnetic components. When a two-axis magnetic sensor is used, the magnetic field strength cannot be determined, so that it is difficult to remove the dynamic magnetic components efficiently.
Consideration is given to the introduction of a three-axis magnetic sensor in order to determine the magnetic field strength. Moreover, to determine an azimuth accurately, it is necessary to correct the terrestrial magnetism vector component detected by the three-axis magnetic sensor with the inclination of the mobile terminal apparatus taken into consideration. The inclination of the mobile terminal apparatus is measured by a tilt angle sensor.